Apparatus for sonic detection



y 2 5- J. R. STEINHOFF 23 3 APPARATUS FOR SONIC DETECTION Fiied April 17, 1942 5 S1etsSheet 1 May 22,1945.

J. R. STEINHOFF APPARATUS FOR SONIC DETECTION 5 Sheets-Sheet Filed April 17, 1942 7 y J. R. STEINHOFF 3 APPARATUS FOR SONIC DETECTION Filed April 17, 1942 5 Sheets-Sheet 5 1945- J. R. STEINVHOFF' 3 3 APPARATUS FOR SONIC DETECTION Filed April 17, 1942 5 sheets-shew, 4

y' z 1945' J. R. STEINHOFF APPARATUS FOR SONIC DETECTION Filed April 17-, 1942 5 Sheets-Sheet 5 onFTo vention;

Patented MayJZZ, 1945 APPARATUS FOR some DETECTION John R'. Steinhofi, WashingtorneD. C.

' Alienation Apr-i117, 1942', serial N61. 439,330

7Claims. (Cl'.177-386) E invention relates to improvements in a method of and apparatus for sonic directional finding and more particularly to a method of and apparatus .for detecting by sound the direction of location cf avessel. I

v Anobject of the invention is to provide a reliable and efiicient method of and apparatus'for providing visual indication of the location of a craft with respect to a detection point.

Another object of the invention is to provide for y direction finding a dynamometer type of instrument' capable of rotating throughthree hundredsixty degrees.

v Another object of the invention is to provide an mproved method for determining the location of a source of sound transmitted under water.

Another object of the invention is to provide andmproved system for determining the direction of an I engine driven vessel bydetecting the under-water sound thereof, including a plurality of submerged directional microphones, an audio amplifier, and an instrument responsive to four series of interspersed signals amplified, rectified and again amplified separately,'including pro-' visio' for four separate D. C. .potentialspropo'rtionalto the series of signals. V

Another object of the invention is conveniently to provide for signalling the presence of a vessel and indicating its direction and movement relative to a detection station.

" Andther object of the invention 'is' to provide e 2 is an enlarged detail showing scherriatic ally retracting mechanism for supporting the microphone housing; Figure} is a horizontal section taken on the s Figure. 4 is'a schematic view showing the coil and rotary scanning mechanism;

mechanism} Figured is asectionltake'n on the line 6+6,

Um 5m. .5

Figure 5 is a perspective view o f the scanning Figure is a view ineleyation showing the face of thedirecti'on indicating instrument;

Figuref8; is a perspective view partly broken away showing the internal rotary and stationary coil portions of the instrument shown in Fi ure 7;

' Figure 9 is a section taken on the line 9-9, Figure 8;.

Figure 10 is a section taken on the line Ill-l0,

Figure 8;";v

Figure 11 is an enlarged fragmentary view in detail showing the electrically conducting bearings for the instrument of Figure 7.

Figure 12 is an elevational view showing one type'of master panel for controlling operation of the system;

Figure 12a is a detail showing an audible alarm whichfmight be employed in the circuit in lieu of the alarm light shown in Figure 12; Figure .13 is a chart showing two imaginary curves depicting the sound characteristics of two vessels and illustrating the utilization of the band pass filters;

Figure 14 is a diagram illustrating the utilization of the system and the chart of Figure 13, and taking simultaneous bearings of two craft;

Figure 15'is a circuit diagram illustrating the principal phases of the electrical aspects of the system;

v o Figure "16 is a diagram depicting utilization of streamline housing [2.

(B) Audio-frequency amplifier l3 (Fig. 15) including rectifier 26 and D. C. voltage amplifier l 5. cc)- Special'apparatus s (Figs. 4-6 and 15) to inductively couple the four microphones to the input I! of the audio-frequency amplifier, separately and in sequence to providefourseries of signals to the input of the amplifier, and simul taneously connect the output N3 of the D. C. amplifier to provide four separate I). C. potentials. (D) Especially designed electrical instrument 20 .(Figs. 1, 7-10 and 15) having a pointer 21 capable of rotating through 360".

The four microphones are located in th streamlined houslng under water. These microphones fllz'z, llb, llcand Hd having directional characteristics are positioned in the streamlined control "panel (not shown) is provided to adjust the various components.

dicator 24 which may be calibrated to provide approximate range. Delayed automatic volume control-.25 allows the amplifier;-to.-be.-maintained at maximum, and decreases the gain proportionately with increasing input voltage. .of..-the eaudioefrequency .amplinenis. rectifiedby a H6 tube 26 as.shovmdnEigure.15,.so.,.as.=-.to.providel-aiD.Q potential,.directmproportionaltosthe audioeirequency voltage applied itogtheamplifier Latsany given instant. .The...v oltage..i's -negative with respect to ground and is applied to thecontrolggrid; 1of.,-the. D. .C. .amp1ifierel 5, which .in,.turn, regulates the flow of plate current through...the resistorel'l. I

The GAG? tube l5 connected as shown in-hfig- .mealfi; has:a;plate .dissipation of-.50. milliarhperes .witln 3526-1 0, gridQVQltaQeeand cutsofiwith aiour volt negative grid-,bias; thereforevariationsinthe .grid;biasnwi1l cause tarvoltage drpp. across.- the; re-

"sistori 2 l proportionalttol variationsofnaudiodrequency intensities applied to the inputmof .the mnl ifierw-z Aa-zfil'o signaLin-put'results iini-arminimum D.-; C. potential between ground and the plate .of the fiAGl-vtube-rl 5; ant-increase, :in signal voltage to the 'iamplifiem results in, a-proportionate; increase tin-MD- .rIC; opotential -on rthe z -platevvof the vfiAG'I tube l5.

.fllherplatez.ofzzithe fiAG'htubev i5 is sequentially connected to fouracondensers-aa-el 30-4,. 30--3 .iA-pnaratus!toresequentially'zconnecting then-in- :puttofiathezamplifier to the four. -microphones-;is

illustrated in Figures '4, 5 and 6.

' Aomotorriirivemshaftfi2-;rotates:switchhontact* rFigure 6. I q

The secondary Windingis ccmleotedsto'the. in-

"putr of the; audiosamplifier. ,-(The-rotary :core .in-

.'di1ctively;;eonnects the zprimaries e3 l separately oandiingthe rollowing seguence primariesa,b c, d, .;.to the secondary winding, w Y a As the-ends. ofitherotaryeor .Biaregfamhedout a to a -9Q? anglefleach primary.ishinductiyelyncow .pled ato the; secondaryator the. duration of L .one- I fourth ci a -qoniplete. reyolliitinn. ".The};primary .coiledareLs'oaarranged;that.couplinglbetween.sc-

io'ridarygand-.onemrimaryccfl ismotJnteriiupted .until; inductive ,cqubhng' is established @with the following-primaryiwiriding"lithe'rotation,ofathe core. y I fqonta'ctffrom 33c to 33a is maintained fduring r1; d 'that prin aryfl'la'isfifiductivel .z'vle. with h se ar winding at a n the The overall amplifier voltage gain is approximately 9,400, and providesaural reception through speakerxBllyandq age-min The output the duration of the inductive coupling of the secondar winding to primary 31b.

Thereafter in sequence, the plate of the GAG? tube I5 will be connected to contact, 330 when primary 310 is inductively coupled to the amplifier input, and also 33d will be connected to 33c when primary 3711 is inductively coupled to the secondary winding. 1

-The four primaries 31a, 31b, 31c and 3111 are "connectedzseparately .to'. the four directive microphones I la, I lb, i la and lhLasshown' in Figure 15, and 'each microphone has a separate gain control. cThe four primary windings 31 are located on stationary cores as shown in Figures 4, 5 and 6,

oppos'ite the 'bucking coils having equal induct- -ance,.and. connected as shown in Figure 15.

The bucking coils are so connected that when I A."C.v.'v61tages are equal in frequency and intensity. in primary 31a and buckingcoil 380. the resulting .nigig'netidflux inthe cores l .will cancel Lout,..and" not create any voltage in the secondary .ivinding.

Bucking coils 38a, 38b, 38c .and' 38d are con- 25 nectedinseries with a noise compensating microphone "40 and each .coil has a separate ,gain

control.

Variable .ban'd passfilter 41in Figure 15 includes. a. frequency. selector switch 5 I, .each tap '30 thereof.;makingconnections,in an inductive .ca-

p'acitynetwork sothat. each" tap sharply. attenuates at a specific resonant frequency. Theten resonantirequencies .are.diyided. oveixthe entire frequency rangeused, .and remotely .operated. "Operationof variable .band. pass. filter M will. be described hereinafter.

.QTheelectrical. indicating instrument2fl (-Figs. .T-eIOandL 15) has ,a scale 42 calibrated in degrees,

sis

40 ...and,the pointer 2| rotates through 360 as shown iniFigure Y7. Thisrneter is of pecial design and ..con'sists ,of;two opposed. dynamometers 43a. and 1.43b,-.the moving coils Maand Mb being mechanicallyattached to each other tbya spacer 45- and to .the.common..pointer-2i. The moving coils- Ma and Mb are energizedby. afixed .D. .C..potential .and'rotate in accordance=with the voltages and -,.polarity'. across the fixed coils Afia and lfib, the movingcoilsbeing. attracted or repelledby the :5 stationary coils.

.When' the equipment .is installed, .the .main

power, switch 89 is. turnedon and; themotor which operatesfthe 'rotary core shaft .32 (Fig. .6) His turned .off.'-..'An audio tone.is.,applied to..the-.four microphones, the sound levelequalto each, each microphongain control being set to maximum. Then, observing the gain. indicator. 24, therotary "(,5 core 3411s: turnedmanually. iNoting.the gain.level *fromeach of'the'iour channels, the gain .o'f'the microphones is decreased until the indicator 24 shows that the four microphones. applyequal voltages tothe input of the amplifier, then the '70 tone is shut on.

When the ship is innormaloperation, and with the rotating core motor still turned dfi,.secondar'y .36 .is inductively coupled with primary,.3la,.-.and the control across" bucking coil 38a is adiustehto zero noise level, using either the gain indicator v the s constantly ob'servedi'.

To'florie'rfate the frequencyfselector switch in variable band pass" fi ter} 4 19,; as adding and sub-- 1 traetingpstepping'relay'is' connected thereto, 1 which i actuated by' a remote pulsing switch 5| v s an unseen vessel 'co'meswithin the range "oif 'the' system, the audio currents increase to acertain intensity, actuating time delay relay v 54 to ligfhfialalm'billb 55for ring alarm bell 5 The; attendant the'ri'operates selector switch 5|, which in turn inserts band pass filters of variable band'ipa'ssfilter ll, thus allowing passage of only a narrow band of frequencies. He looks at direc{- tion me er andfturn's the selector switch. If meterpo'interZl remains in the same position, thefpresence of but one craft is established, and its true bearing isindicatedin line with the pointer. lfiinrotating the selector switch the pointer shoi'ildswing th'e j'pres'ence' of more than one craftis established Bycalibratingthe selector switch to express the frequencies being amplified ateach stop and? so by notingthe level of signalbeing 'picked up asseen' on gain indicator 24, it is'practicable to iden-[ tify ci'aft by type, If curves "were; plotted for different-vessels and their sounds, no two vessels would have identical curvesl'j For example, sound waves frizimfa' large'tanker -B have peak freq'uencies-in lower range of the audio spectrum; where as a 'submarine'A'will register a peak'in the neigh I 3 borhood-of 16 or 1'7 M cycles, as indicated by v I curves' Al and BI, respctivelyyse'e Fig. 13. 1 40 Figure 13 'is a graph illustrating th e amplifyingcharacter'isti'cs of the audio-amplifier andalso showing' thetwo'imaginary curves 'depictingco 1 parative intensities at different frequencies from two crafts 'within' the range ofthe'detecto'r' systemn w-ith-the detectionapparatus installed on craft 50,fFigures land 14; unseen'craft A and B 3 will 'be' noted." Curve Al indicates sound radiatedby craft} A whilecurve B l indicates sounds radiliteinote control panel 52 of Figure '12 marryingselector 'sv'r'ith St is pr'c'ivi'ded with 12 stops, the first thereof indicating the OFF position. When selector switch 5| (Figure 12) is placed on stop I, the amplifier has the characteristics of curve Cl, being relatively flat from 30 to 20,000 cycles. ,At

stop 2, a band pass filter is inserted in the amplifier so as to depict the characteristics of curve C2 allowing the amplification of only the frequencies from 350 to 650 cycles and rejecting all other frequencies. Moving selector switch to stop 3 changes the frequency selector switch in the-am;

plifier to another band pass filter resulting in] curve C3; and utilization of the stops 4 to II suc cessively respectively connect band pass filters to produce curves C4 to CH sequentially.

An essential element in the present invention is meter or instrument 20, similar to the device covered in my copending application Serial No. 417,835, filed Nov. 4, 1941, and similar to a dynamometer in construction. Moving coils wand 44b rotate within two stationary coils 46a. and 4B b,their movement being governed by magnetic energies only, no springs being used thereini Two pivots 61a, and 6 lb are attached to the moving coils as-shownin Fig. 8, and the pointer 2i is fixedflto the'top pivot 61a. to extend at a 45 degree angle to the moving coils. Pivots Bio and b rotate freely in adjusting screws, the latter being recessedwith communicating areas fixedly receiving a'bored jewel 64 and mercury P for maintaining electrical contact with a fine wire Q of platinuin'er other conductive material on the tip of the pivot, see Fig. 11. As the moving coils must rotatethrough three hundred sixty degrees, it is v necessary to mount the top screw in glass R on the'indicatortop. A fine wire R! is connected to the 'screw'and extended'across the glass, see

Fig. 7.

As shown in the wiring diagram of Fig; 15, a fixed potential is applied to the moving coils Ma andfllnand the resulting magnetic lines of force are always in the same direction and of the same intensity. The moving coils are attracted to'or repelled from the stationary coils by a force clepending upon the direction and amount of current flowing through the stationary coils, thereby causing the moving system of the instrument to rotateto'a position corresponding to the directional orientation of-the signals.

"I'o damp the instrument pointer 21 an aluminum disc 10 is fixed to pivot lila to rotate in the magnetic field of permanent magnet l l, as shown in Fig. 8.

Asthe microphone housing must be located below th'h-iill i1; is retractable by the mechanism of Fig. 2. Well 8| in the hull contains plunger 82 forced-down by pressure in chamber 83 through of'the housing by pressure of the water.

What Iv'claim is:

1. Irra sonic direction finding slevice, four di-. rectio'nally responsive microphones divergently directed at an angle of one to the other in a horizontal plane, a direction indicator responsive to signals from said microphones, means for impressing signals from each of said microphones" upon saidiindicator in a sense directionally oriented in'correspondence with the direction of said microphones, a further microphone positioned to receive substantially only station noise, and means v for reducing the signals from each of said first F "microphones in proportion tothe strength of the signal iromsaid further microphone.

2. In a sonic direction finding device, foundire'ctiorlally responsive microphones divergently directed in a horizontal plane, a direction indicator responsive to signals from said microphones, means for impressing signals from each of said microphones upon said indicator in a sense directionally oriented in correspondence with the direction of said microphones, including four primary windings each connected to one of said microphones and positioned on individual cores around a secondary winding, a rotatable core inductively coupling each primary winding to the secondary winding in sequence, and means for connecting said secondary winding to said 'direction indicator in said directional sense in synchronism with the rotation of said core.

3. In a sonic direction finding device, four directionally responsive microphones divergently directed in a horizontal plane, a direction indicator responsive to signals from said microphones,

means for impressing signals from each of said microphones upon said indicator in a sense directionally oriented in correspondence with the direction of said microphones, including four primamwindi-nes each connected to one of said zmiomphones and positioned on individual cores arounda secondary winding, a rotatable core inductivelyfcoupling each primary winding .to the secondary winding insequence, a further microphone positioned to receive substantially only station noise, coils equal in inductance and opposite in phase-to said primary windings and connected to'saidiunther-,microphone'mounted on each of :said individual cores to induce therein a counter magnetic ilux, and means'for connecting said seciondary winding to said direction indicator in said directional sense in synchronism with .the'rotation of said core. J

r Inasonic-direction finding device, fourdirectionally responsive microphones divergently directed'at zan angle of,90 one to-the other in a --l -iorizonta1- plane, .a direction indicator responsive-to'signa-ls from said microphones, means for impressing signals from each .ofsaid microphones ruponsaid indicator in a sense dire'ctionallyoriientedzin correspondence-with the direction of said .inicrophones, including an audio frequency am- .plifier for said signals, .a-plurality of band pass filterstuned to di-iierent audio frequencies, and means tor separately selecting said filters to distinguishibetweenz two or more sound'sources by the distinctive frequency characteristics of said sources. i

5. .In a sonic direction finding device, four directionally responsive microphones divergentily directed at an-angle of 90 one -tothe other in .-a horizontal plane, a direction indicator responsive toxsignals from said microphones, means for impressing signals from each of said microphones upon :said indicator, including an Hau'dio, frequency amplifier, :switch' means successively connecting said microphones to said audio frequency amplifier, means for-rectifying the "output of said amplifier to provide unidirectional potentials "proportional to the signals from said microphones, -a grid-controlled-vacuum tube having a resistance-in the plate-circuit, ,means for impressing said unidirectional potentials on the grid ofcsaid "tube, and switch meansfor impressing the resultant potentials from the plate of said microphones and in-synchronism with said first 'switchianeans.

6. In a sonic direction finding device, four'directionaliy' responsive microphones: divergently ,directedi in aihorizontal plane, a direction indicator, responsive, to signals from said microphones, means for impressing signals from each of said, microphones upon said indicator in a sense directionally oriented in correspondence with thedirection of. said microphones, including four primarywindings each connected to one of said microphones and positioned on individual cores around .a secondary winding, a rotatable core inductively coupling each primary Winding to the secondary winding in sequence, means connectingsaid secondary winding to said direction indicator, including an. audio frequency amplifienmeans for rectifying the output of said amplifier, and a quadripole rotary switch mechanically connected to said rotatable core and electrically connecting the rectified output of saiduamplifier, with said direction indicator in different successive directional orientation in synchronism with the coupling effected by said coretoprovide a series of unidirectional potensensedirectionally oriented in correspondence .withjthedirection of said microphones, including ,four primarywindings each connected to one of; said gmic'rophonesand positioned on individual cores around a secondary winding, a rotatable ,core inductively coupling each primary winding .to thesecondary winding in sequence means connecting said secondary winding to'said direction indicator, -.including an audio frequency amplifier, means for rectifying'the output of said amplifier',v a quadripole rotary switch mechanically connected to said rotatable core and electrically connecting the rectified output of said amplifier with said direction indicator in different successive' directional orientation in synchronism with the coupling efiected bysaid core to provide a series of, unidirectional potentials proportionate .to the ,fourinterspe-rsed series of signals induced in said secondary winding, and condensers connected ,to;eachpole of said rotary switch to maintain the value of the potentials during the period that said; poles are disconnected.

- JOHN R. STEINHOFF. 

